#region Copyright notice and license

// Copyright 2018 gRPC authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#endregion

using System;
using System.Reflection;
using System.Threading.Tasks;
using Grpc.Core.Internal;

namespace Grpc.Core.Interceptors;

/// <summary>
/// Serves as the base class for gRPC interceptors.
/// </summary>
public abstract class Interceptor
{
    /// <summary>
    /// Represents a continuation for intercepting simple blocking invocations.
    /// A delegate of this type is passed to the BlockingUnaryCall method
    /// when an outgoing invocation is being intercepted and calling the
    /// delegate will invoke the next interceptor in the chain, or the underlying
    /// call invoker if called from the last interceptor. The interceptor is
    /// allowed to call it zero, one, or multiple times, passing it the appropriate
    /// context and request values as it sees fit.
    /// </summary>
    /// <typeparam name="TRequest">Request message type for this invocation.</typeparam>
    /// <typeparam name="TResponse">Response message type for this invocation.</typeparam>
    /// <param name="request">The request value to continue the invocation with.</param>
    /// <param name="context">
    /// The <see cref="Grpc.Core.Interceptors.ClientInterceptorContext{TRequest, TResponse}"/>
    /// instance to pass to the next step in the invocation process.
    /// </param>
    /// <returns>
    /// The response value of the invocation to return to the caller.
    /// The interceptor can choose to return the return value of the
    /// continuation delegate or an arbitrary value as it sees fit.
    /// </returns>
    public delegate TResponse BlockingUnaryCallContinuation<TRequest, TResponse>(TRequest request, ClientInterceptorContext<TRequest, TResponse> context)
        where TRequest : class
        where TResponse : class;

    /// <summary>
    /// Represents a continuation for intercepting simple asynchronous invocations.
    /// A delegate of this type is passed to the AsyncUnaryCall method
    /// when an outgoing invocation is being intercepted and calling the
    /// delegate will invoke the next interceptor in the chain, or the underlying
    /// call invoker if called from the last interceptor. The interceptor is
    /// allowed to call it zero, one, or multiple times, passing it the appropriate
    /// request value and context as it sees fit.
    /// </summary>
    /// <typeparam name="TRequest">Request message type for this invocation.</typeparam>
    /// <typeparam name="TResponse">Response message type for this invocation.</typeparam>
    /// <param name="request">The request value to continue the invocation with.</param>
    /// <param name="context">
    /// The <see cref="Grpc.Core.Interceptors.ClientInterceptorContext{TRequest, TResponse}"/>
    /// instance to pass to the next step in the invocation process.
    /// </param>
    /// <returns>
    /// An instance of <see cref="Grpc.Core.AsyncUnaryCall{TResponse}" />
    /// representing an asynchronous invocation of a unary RPC.
    /// The interceptor can choose to return the same object returned from
    /// the continuation delegate or an arbitrarily constructed instance as it sees fit.
    /// </returns>
    public delegate AsyncUnaryCall<TResponse> AsyncUnaryCallContinuation<TRequest, TResponse>(TRequest request, ClientInterceptorContext<TRequest, TResponse> context)
        where TRequest : class
        where TResponse : class;

    /// <summary>
    /// Represents a continuation for intercepting asynchronous server-streaming invocations.
    /// A delegate of this type is passed to the AsyncServerStreamingCall method
    /// when an outgoing invocation is being intercepted and calling the
    /// delegate will invoke the next interceptor in the chain, or the underlying
    /// call invoker if called from the last interceptor. The interceptor is
    /// allowed to call it zero, one, or multiple times, passing it the appropriate
    /// request value and context as it sees fit.
    /// </summary>
    /// <typeparam name="TRequest">Request message type for this invocation.</typeparam>
    /// <typeparam name="TResponse">Response message type for this invocation.</typeparam>
    /// <param name="request">The request value to continue the invocation with.</param>
    /// <param name="context">
    /// The <see cref="Grpc.Core.Interceptors.ClientInterceptorContext{TRequest, TResponse}"/>
    /// instance to pass to the next step in the invocation process.
    /// </param>
    /// <returns>
    /// An instance of <see cref="Grpc.Core.AsyncServerStreamingCall{TResponse}" />
    /// representing an asynchronous invocation of a server-streaming RPC.
    /// The interceptor can choose to return the same object returned from
    /// the continuation delegate or an arbitrarily constructed instance as it sees fit.
    /// </returns>
    public delegate AsyncServerStreamingCall<TResponse> AsyncServerStreamingCallContinuation<TRequest, TResponse>(TRequest request, ClientInterceptorContext<TRequest, TResponse> context)
        where TRequest : class
        where TResponse : class;

    /// <summary>
    /// Represents a continuation for intercepting asynchronous client-streaming invocations.
    /// A delegate of this type is passed to the AsyncClientStreamingCall method
    /// when an outgoing invocation is being intercepted and calling the
    /// delegate will invoke the next interceptor in the chain, or the underlying
    /// call invoker if called from the last interceptor. The interceptor is
    /// allowed to call it zero, one, or multiple times, passing it the appropriate
    /// request value and context as it sees fit.
    /// </summary>
    /// <typeparam name="TRequest">Request message type for this invocation.</typeparam>
    /// <typeparam name="TResponse">Response message type for this invocation.</typeparam>
    /// <param name="context">
    /// The <see cref="Grpc.Core.Interceptors.ClientInterceptorContext{TRequest, TResponse}"/>
    /// instance to pass to the next step in the invocation process.
    /// </param>
    /// <returns>
    /// An instance of <see cref="Grpc.Core.AsyncClientStreamingCall{TRequest, TResponse}" />
    /// representing an asynchronous invocation of a client-streaming RPC.
    /// The interceptor can choose to return the same object returned from
    /// the continuation delegate or an arbitrarily constructed instance as it sees fit.
    /// </returns>
    public delegate AsyncClientStreamingCall<TRequest, TResponse> AsyncClientStreamingCallContinuation<TRequest, TResponse>(ClientInterceptorContext<TRequest, TResponse> context)
        where TRequest : class
        where TResponse : class;

    /// <summary>
    /// Represents a continuation for intercepting asynchronous duplex invocations.
    /// A delegate of this type is passed to the AsyncDuplexStreamingCall method
    /// when an outgoing invocation is being intercepted and calling the
    /// delegate will invoke the next interceptor in the chain, or the underlying
    /// call invoker if called from the last interceptor. The interceptor is
    /// allowed to call it zero, one, or multiple times, passing it the appropriate
    /// request value and context as it sees fit.
    /// </summary>
    /// <param name="context">
    /// The <see cref="Grpc.Core.Interceptors.ClientInterceptorContext{TRequest, TResponse}"/>
    /// instance to pass to the next step in the invocation process.
    /// </param>
    /// <returns>
    /// An instance of <see cref="Grpc.Core.AsyncDuplexStreamingCall{TRequest, TResponse}" />
    /// representing an asynchronous invocation of a duplex-streaming RPC.
    /// The interceptor can choose to return the same object returned from
    /// the continuation delegate or an arbitrarily constructed instance as it sees fit.
    /// </returns>
    public delegate AsyncDuplexStreamingCall<TRequest, TResponse> AsyncDuplexStreamingCallContinuation<TRequest, TResponse>(ClientInterceptorContext<TRequest, TResponse> context)
        where TRequest : class
        where TResponse : class;

    /// <summary>
    /// Intercepts a blocking invocation of a simple remote call.
    /// </summary>
    /// <param name="request">The request message of the invocation.</param>
    /// <param name="context">
    /// The <see cref="Grpc.Core.Interceptors.ClientInterceptorContext{TRequest, TResponse}"/>
    /// associated with the current invocation.
    /// </param>
    /// <param name="continuation">
    /// The callback that continues the invocation process.
    /// This can be invoked zero or more times by the interceptor.
    /// The interceptor can invoke the continuation passing the given
    /// request value and context arguments, or substitute them as it sees fit.
    /// </param>
    /// <returns>
    /// The response message of the current invocation.
    /// The interceptor can simply return the return value of the
    /// continuation delegate passed to it intact, or an arbitrary
    /// value as it sees fit.
    /// </returns>
    public virtual TResponse BlockingUnaryCall<TRequest, TResponse>(TRequest request, ClientInterceptorContext<TRequest, TResponse> context, BlockingUnaryCallContinuation<TRequest, TResponse> continuation)
        where TRequest : class
        where TResponse : class
    {
        return continuation(request, context);
    }

    /// <summary>
    /// Intercepts an asynchronous invocation of a simple remote call.
    /// </summary>
    /// <param name="request">The request message of the invocation.</param>
    /// <param name="context">
    /// The <see cref="Grpc.Core.Interceptors.ClientInterceptorContext{TRequest, TResponse}"/>
    /// associated with the current invocation.
    /// </param>
    /// <param name="continuation">
    /// The callback that continues the invocation process.
    /// This can be invoked zero or more times by the interceptor.
    /// The interceptor can invoke the continuation passing the given
    /// request value and context arguments, or substitute them as it sees fit.
    /// </param>
    /// <returns>
    /// An instance of <see cref="Grpc.Core.AsyncUnaryCall{TResponse}" />
    /// representing an asynchronous unary invocation.
    /// The interceptor can simply return the return value of the
    /// continuation delegate passed to it intact, or construct its
    /// own substitute as it sees fit.
    /// </returns>
    public virtual AsyncUnaryCall<TResponse> AsyncUnaryCall<TRequest, TResponse>(TRequest request, ClientInterceptorContext<TRequest, TResponse> context, AsyncUnaryCallContinuation<TRequest, TResponse> continuation)
        where TRequest : class
        where TResponse : class
    {
        return continuation(request, context);
    }

    /// <summary>
    /// Intercepts an asynchronous invocation of a streaming remote call.
    /// </summary>
    /// <param name="request">The request message of the invocation.</param>
    /// <param name="context">
    /// The <see cref="Grpc.Core.Interceptors.ClientInterceptorContext{TRequest, TResponse}"/>
    /// associated with the current invocation.
    /// </param>
    /// <param name="continuation">
    /// The callback that continues the invocation process.
    /// This can be invoked zero or more times by the interceptor.
    /// The interceptor can invoke the continuation passing the given
    /// request value and context arguments, or substitute them as it sees fit.
    /// </param>
    /// <returns>
    /// An instance of <see cref="Grpc.Core.AsyncServerStreamingCall{TResponse}" />
    /// representing an asynchronous server-streaming invocation.
    /// The interceptor can simply return the return value of the
    /// continuation delegate passed to it intact, or construct its
    /// own substitute as it sees fit.
    /// </returns>
    public virtual AsyncServerStreamingCall<TResponse> AsyncServerStreamingCall<TRequest, TResponse>(TRequest request, ClientInterceptorContext<TRequest, TResponse> context, AsyncServerStreamingCallContinuation<TRequest, TResponse> continuation)
        where TRequest : class
        where TResponse : class
    {
        return continuation(request, context);
    }

    /// <summary>
    /// Intercepts an asynchronous invocation of a client streaming call.
    /// </summary>
    /// <param name="context">
    /// The <see cref="Grpc.Core.Interceptors.ClientInterceptorContext{TRequest, TResponse}"/>
    /// associated with the current invocation.
    /// </param>
    /// <param name="continuation">
    /// The callback that continues the invocation process.
    /// This can be invoked zero or more times by the interceptor.
    /// The interceptor can invoke the continuation passing the given
    /// context argument, or substitute as it sees fit.
    /// </param>
    /// <returns>
    /// An instance of <see cref="Grpc.Core.AsyncClientStreamingCall{TRequest, TResponse}" />
    /// representing an asynchronous client-streaming invocation.
    /// The interceptor can simply return the return value of the
    /// continuation delegate passed to it intact, or construct its
    /// own substitute as it sees fit.
    /// </returns>
    public virtual AsyncClientStreamingCall<TRequest, TResponse> AsyncClientStreamingCall<TRequest, TResponse>(ClientInterceptorContext<TRequest, TResponse> context, AsyncClientStreamingCallContinuation<TRequest, TResponse> continuation)
        where TRequest : class
        where TResponse : class
    {
        return continuation(context);
    }

    /// <summary>
    /// Intercepts an asynchronous invocation of a duplex streaming call.
    /// </summary>
    /// <param name="context">
    /// The <see cref="Grpc.Core.Interceptors.ClientInterceptorContext{TRequest, TResponse}"/>
    /// associated with the current invocation.
    /// </param>
    /// <param name="continuation">
    /// The callback that continues the invocation process.
    /// This can be invoked zero or more times by the interceptor.
    /// The interceptor can invoke the continuation passing the given
    /// context argument, or substitute as it sees fit.
    /// </param>
    /// <returns>
    /// An instance of <see cref="Grpc.Core.AsyncDuplexStreamingCall{TRequest, TResponse}" />
    /// representing an asynchronous duplex-streaming invocation.
    /// The interceptor can simply return the return value of the
    /// continuation delegate passed to it intact, or construct its
    /// own substitute as it sees fit.
    /// </returns>
    public virtual AsyncDuplexStreamingCall<TRequest, TResponse> AsyncDuplexStreamingCall<TRequest, TResponse>(ClientInterceptorContext<TRequest, TResponse> context, AsyncDuplexStreamingCallContinuation<TRequest, TResponse> continuation)
        where TRequest : class
        where TResponse : class
    {
        return continuation(context);
    }

    /// <summary>
    /// Server-side handler for intercepting and incoming unary call.
    /// </summary>
    /// <typeparam name="TRequest">Request message type for this method.</typeparam>
    /// <typeparam name="TResponse">Response message type for this method.</typeparam>
    /// <param name="request">The request value of the incoming invocation.</param>
    /// <param name="context">
    /// An instance of <see cref="Grpc.Core.ServerCallContext" /> representing
    /// the context of the invocation.
    /// </param>
    /// <param name="continuation">
    /// A delegate that asynchronously proceeds with the invocation, calling
    /// the next interceptor in the chain, or the service request handler,
    /// in case of the last interceptor and return the response value of
    /// the RPC. The interceptor can choose to call it zero or more times
    /// at its discretion.
    /// </param>
    /// <returns>
    /// A future representing the response value of the RPC. The interceptor
    /// can simply return the return value from the continuation intact,
    /// or an arbitrary response value as it sees fit.
    /// </returns>
    public virtual Task<TResponse> UnaryServerHandler<TRequest, TResponse>(TRequest request, ServerCallContext context, UnaryServerMethod<TRequest, TResponse> continuation)
        where TRequest : class
        where TResponse : class
    {
        return continuation(request, context);
    }

    /// <summary>
    /// Server-side handler for intercepting client streaming call.
    /// </summary>
    /// <typeparam name="TRequest">Request message type for this method.</typeparam>
    /// <typeparam name="TResponse">Response message type for this method.</typeparam>
    /// <param name="requestStream">The request stream of the incoming invocation.</param>
    /// <param name="context">
    /// An instance of <see cref="Grpc.Core.ServerCallContext" /> representing
    /// the context of the invocation.
    /// </param>
    /// <param name="continuation">
    /// A delegate that asynchronously proceeds with the invocation, calling
    /// the next interceptor in the chain, or the service request handler,
    /// in case of the last interceptor and return the response value of
    /// the RPC. The interceptor can choose to call it zero or more times
    /// at its discretion.
    /// </param>
    /// <returns>
    /// A future representing the response value of the RPC. The interceptor
    /// can simply return the return value from the continuation intact,
    /// or an arbitrary response value as it sees fit. The interceptor has
    /// the ability to wrap or substitute the request stream when calling
    /// the continuation.
    /// </returns>
    public virtual Task<TResponse> ClientStreamingServerHandler<TRequest, TResponse>(IAsyncStreamReader<TRequest> requestStream, ServerCallContext context, ClientStreamingServerMethod<TRequest, TResponse> continuation)
        where TRequest : class
        where TResponse : class
    {
        return continuation(requestStream, context);
    }

    /// <summary>
    /// Server-side handler for intercepting server streaming call.
    /// </summary>
    /// <typeparam name="TRequest">Request message type for this method.</typeparam>
    /// <typeparam name="TResponse">Response message type for this method.</typeparam>
    /// <param name="request">The request value of the incoming invocation.</param>
    /// <param name="responseStream">The response stream of the incoming invocation.</param>
    /// <param name="context">
    /// An instance of <see cref="Grpc.Core.ServerCallContext" /> representing
    /// the context of the invocation.
    /// </param>
    /// <param name="continuation">
    /// A delegate that asynchronously proceeds with the invocation, calling
    /// the next interceptor in the chain, or the service request handler,
    /// in case of the last interceptor and the interceptor can choose to
    /// call it zero or more times at its discretion. The interceptor has
    /// the ability to wrap or substitute the request value and the response stream
    /// when calling the continuation.
    /// </param>
    public virtual Task ServerStreamingServerHandler<TRequest, TResponse>(TRequest request, IServerStreamWriter<TResponse> responseStream, ServerCallContext context, ServerStreamingServerMethod<TRequest, TResponse> continuation)
        where TRequest : class
        where TResponse : class
    {
        return continuation(request, responseStream, context);
    }

    /// <summary>
    /// Server-side handler for intercepting bidirectional streaming calls.
    /// </summary>
    /// <typeparam name="TRequest">Request message type for this method.</typeparam>
    /// <typeparam name="TResponse">Response message type for this method.</typeparam>
    /// <param name="requestStream">The request stream of the incoming invocation.</param>
    /// <param name="responseStream">The response stream of the incoming invocation.</param>
    /// <param name="context">
    /// An instance of <see cref="Grpc.Core.ServerCallContext" /> representing
    /// the context of the invocation.
    /// </param>
    /// <param name="continuation">
    /// A delegate that asynchronously proceeds with the invocation, calling
    /// the next interceptor in the chain, or the service request handler,
    /// in case of the last interceptor and the interceptor can choose to
    /// call it zero or more times at its discretion. The interceptor has
    /// the ability to wrap or substitute the request and response streams
    /// when calling the continuation.
    /// </param>
    public virtual Task DuplexStreamingServerHandler<TRequest, TResponse>(IAsyncStreamReader<TRequest> requestStream, IServerStreamWriter<TResponse> responseStream, ServerCallContext context, DuplexStreamingServerMethod<TRequest, TResponse> continuation)
        where TRequest : class
        where TResponse : class
    {
        return continuation(requestStream, responseStream, context);
    }
}
